Cigarette smoking is common; approximately 25% of adults over 18 years of age are regular smokers. Craving is an important component of the symptoms experienced during smoking cessation and it considered a crucial factor in relapse. There is some evidence that menstrual cycle may impact smoking and relapse for women, but this has not been well explored. Hence, menstrual cycle phase may be an important modulator of craving and may contribute in relapse among women attempting smoking cessation. There is also data suggesting that there are different subjective and physiological responses to nicotine during different phases of the menstrual cycle, but little work has been done in exploring the effect of menstrual cycle phases on smoking cue-reactivity. Research on the effect of menstrual cycle phase on smoking cue-reactivity may be especially important for smoking cessation treatment as it is common practice in smoking cessation programs to set a quit date prior to the quit attempt. Knowledge about the menstrual cycle phase differences in cue-reactivity may help in setting an optimal quit date for women in order to maximize the chances of successful smoking cessation The specific aims of the proposed project are: 1. To examine the effect of menstrual cycle phase on reactivity to "in vivo" cigarette smoking cues and negative affect-inducing cues in nicotine-dependent women. 2. To examine gender differences in the reactivity to "in vivo" cigarette smoking cues and negative-affect inducing cues in nicotine-dependent men and women. The proposed project will use both in vivo smoking cues, as well as negative affect/stress cues to explore smoking cue-reactivity in female smokers during four biologically verified menstrual phases. Female cigarette smokers' reactivity will also be compared to the reactivity of male cigarette smokers who will be tested in a similar protocol. Both subjective craving and mood responses, as well as physiological responses (e.g., real-time heart rate, galvanic skin conductance) will be measured during the study. This information may help in designing specific smoking-cessation approaches for nicotine-dependent women.